Non-plugging d.c. plasma gun

ABSTRACT

A plasma gun system comprising: a plasma gun comprising an outlet, wherein the plasma gun is configured to generate a plasma stream and provide the plasma stream to the outlet; and a plasma gun extension assembly configured to be coupled to the plasma gun, wherein the plasma gun extension assembly comprises an extension chamber and a port, the extension chamber having an interior diameter defined by a chamber wall and being configured to receive the plasma stream from the outlet of the plasma gun and to enable the plasma stream to expand upon entering the extension chamber, and the port being configured to introduce a powder to the expanded plasma stream at a location outside of the plasma gun.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application Ser. No. 61/284,329, filed Dec. 15, 2009 and entitled “MATERIALS PROCESSING,” which is hereby incorporated herein by reference in its entirety as if set forth herein.

FIELD OF THE INVENTION

The present invention relates to the field of powder material processing. More specifically, the present invention relates to powder material processing using a plasma gun.

BACKGROUND OF THE INVENTION

FIG. 1 illustrates one embodiment of a plasma gun 100 used to process powder material. The plasma gun 100 is a DC plasma torch including a male electrode 120 and a female electrode 130. A power supply (not shown) is connected to the male electrode 120 and the female electrode 130 and delivers power through the plasma gun 100 by passing current across the gap 160 between the male electrode 120 and the female electrode 130. Furthermore, the plasma gun 100 includes a gas inlet 140 fluidly coupled to the gap 160 and configured to receive a working gas. The plasma gun 100 also includes a plasma outlet 150 fluidly coupled to the gap 160 on the opposite side of the plasma gun 100 from the gas inlet 140 and configured to provide a path through which a plasma stream 180 can be expelled from the plasma gun 100.

During operation, working gas flows through the gas inlet 140, through the gap 160 and out of the outlet 150. At the same time, power is supplied to the plasma gun 100. The current arcing across the gap 160 energizes the working gas and forms plasma 180, which flows out of the outlet 150. Powdered material 110 is fed into the plasma stream 180 through a channel 170 that is fluidly coupled to the pathway between the gap 160 and the plasma outlet 150 via a port 175 to the pathway. The plasma stream 180 entrains and works on the powder, forming a plasma powder mixture that flows out of the plasma gun 100 through the outlet 150.

There is a problem with this configuration of the plasma gun. The radiant and conductive heat of the plasma 180 melts the powder particles 110 before they get all the way down the channel 170 and exit the port 175 into the pathway between the gap 160 and the outlet 150. As a result, the melted particles agglomerate and stick to the sides of the channel 170 and the port 175, clogging them up. Consequently, operation of the plasma gun has to be stopped until it is cleaned, which results in a significant loss of productivity.

SUMMARY OF THE INVENTION

In one aspect of the present invention, a method of using a plasma gun system is provided. The method comprises generating a plasma stream using a plasma gun, wherein the plasma stream flows through an outlet of the plasma gun and into an extension chamber having an interior diameter defined by a chamber wall. The plasma stream expands upon entering the extension chamber. A powder flows into the expanded plasma stream in the extension chamber via a port fluidly coupled to the extension chamber. The port introduces the powder to the expanded plasma stream at a location outside of the plasma gun.

In another aspect of the present invention, a plasma gun system is provided. The plasma gun system comprises a plasma gun and a plasma gun extension assembly. The plasma gun comprises an outlet and is configured to generate a plasma stream and provide the plasma stream to the outlet. The plasma gun extension assembly is configured to be coupled to the plasma gun. The plasma gun extension assembly comprises an extension chamber and a port. The extension chamber has an interior diameter defined by a chamber wall and is configured to receive the plasma stream from the outlet of the plasma gun and to enable the plasma stream to expand upon entering the extension chamber. The port is configured to introduce a powder to the expanded plasma stream at a location outside of the plasma gun.

In some embodiments, the port is disposed on a faceplate that is coupled between the plasma gun and the extension chamber. In some embodiments, the faceplate comprises a circular ring shape and the outlet of the plasma gun is aligned with the center of the faceplate to enable the plasma stream to pass the faceplate and flow into the extension chamber. In some embodiments, the faceplate comprises copper.

In some embodiments, the chamber wall comprises a ceramic material. In some embodiments, the chamber wall comprises boron nitride. In some embodiments, the chamber wall comprises a substantially tubular shape. In some embodiments, a stainless steel sheath is coupled to the faceplate and around the chamber wall.

In some embodiments, the faceplate is configured to be coupled to the chamber wall prior to being coupled to the plasma gun, thereby allowing the faceplate and the chamber wall to be coupled to the plasma gun and de-coupled from the plasma gun as a single unit. In some embodiments, the faceplate, the chamber wall, and the plasma gun are configured to be coupled together using one or more threaded fasteners.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates one embodiment of a plasma gun used to process powder material.

FIG. 2 illustrates one embodiment of a plasma gun and an extension assembly used to process powder material in accordance with the principles of the present invention.

FIG. 3 illustrates one embodiment of method of using a plasma gun and an extension assembly to process powder material in accordance with the principles of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The following description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the described embodiments will be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. Thus, the present invention is not intended to be limited to the embodiment shown but is to be accorded the widest scope consistent with the principles and features described herein.

This disclosure refers to both particles and powders. These two terms are equivalent, except for the caveat that a singular “powder” refers to a collection of particles. The present invention may apply to a wide variety of powders and particles. Powders that fall within the scope of the present invention may include, but are not limited to, any of the following: (a) nano-structured powders(nano-powders), having an average grain size less than 250 nanometers and an aspect ratio between one and one million; (b) submicron powders, having an average grain size less than 1 micron and an aspect ratio between one and one million; (c) ultra-fine powders, having an average grain size less than 100 microns and an aspect ratio between one and one million; and (d) fine powders, having an average grain size less than 500 microns and an aspect ratio between one and one million.

FIG. 2 illustrates one embodiment of a plasma gun system 200 comprising a plasma gun 202 and an extension assembly 204. Generally, the plasma gun system 200 operates as a reactor, producing an output comprising particles within a gas stream.

In some embodiments, the plasma gun 202 includes a male electrode 220 and a female electrode 230 encased within an insulating housing 205. A power supply (not shown) is connected to the male electrode 220 and the female electrode 230 and delivers power through the plasma gun 202 by passing current across the gap 260 between the male electrode 220 and the female electrode 230. A variety of different means can be employed to deliver this energy, including, but not limited to, DC coupling, capacitive coupling, inductive coupling, and resonant coupling.

Furthermore, the plasma gun 202 includes a gas inlet 240 fluidly coupled to the gap 260 and configured to receive a working gas. The plasma gun 202 also includes a plasma outlet 250 fluidly coupled to the gap 260 on the opposite side of the plasma gun 202 from the gas inlet 240 and configured to provide a path through which a plasma stream 280 can be expelled from the plasma gun 202.

As the plasma stream 280 exits the plasma gun 202, it enters the extension chamber 285 of the extension assembly 204. The diameter of the extension chamber 285 is greater than the diameter of the pathway between the gap 260 and the plasma outlet 250. Therefore, the plasma stream 280 expands as it enters the extension chamber 285. A powder material 210 flows into the expanded plasma stream 280 in the extension chamber 285 via a port 275 that is fluidly coupled to the extension chamber 285. The port 275 introduces the powder 210 to the expanded plasma stream 280 at a location outside of the plasma gun 202.

In some embodiments, the extension assembly 204 comprises a faceplate 290 and an extension tube 294. It is noted that FIG. 2 displays faceplate 290 as a patterned component. However, the purpose of this patterning is to help distinguish the faceplate 290 from the other components and should not be used to limit the scope of the present invention.

In some embodiments, the port 275 is disposed on the faceplate 290, which is coupled between the plasma gun 202 and the extension chamber 285. In some embodiments, the faceplate 290 comprises a circular ring shape and the outlet 250 of the plasma gun 202 is aligned with the center of the faceplate 290 to enable the plasma stream 280 to pass the faceplate 290 and flow into the extension chamber 285. In some embodiments, the faceplate 290 is configured to fit securely around a protruding end portion of the plasma gun 202, such as the end of female electrode 230 as shown in FIG. 2. In some embodiments, the faceplate 290 is formed from a metal material. In some embodiments, the faceplate 290 comprises copper.

As previously discussed, the port 275 is configured to introduce the powder 210 to the expanded plasma stream 280 at a location outside of the plasma gun 202. In some embodiments, the port 275 is configured to enable the powder 210 to flow into the chamber 285, and into the plasma stream 280, at an angle that is configured in the general direction of the flow of the plasma stream 280 (i.e., away from the plasma gun 202). In some embodiments, the port 275 is configured to enable the powder 210 to flow into the chamber 285, and into the plasma stream 280, at an angle that is configured in the general direction of the flow of the plasma stream 280 (i.e., away from the plasma gun 202) and towards the center of the chamber 285. For example, in some embodiments, the port 275 is configured to enable the powder 210 to flow into the chamber 285, and into the plasma stream 280, towards the center of the chamber 285 at an angle approximately 45-degrees from the interior wall 294 of the chamber 285, as shown in FIG. 2.

In some embodiments, the powder material 210 is flows to the port 275 through a channel 270 that is fluidly coupled to the port 275. In some embodiments, the channel 270 is disposed within the faceplate 290. In some embodiments, the powder material 210 is supplied to the channel 270 via a feeding tube 277, which can be coupled to or formed integrally with the faceplate 290. In some embodiments, a valve (not shown) is disposed on the feeding tube 277 or on the faceplate 290 to control the flow of powder material through the channel 270 and port 275 and into the chamber 285.

In some embodiments, the extension chamber 285 has an interior diameter defined by the chamber wall 294. In some embodiments, the chamber wall 294 comprises a ceramic material. In some embodiments, the chamber wall 294 comprises boron nitride. In some embodiments, the chamber wall 294 comprises a substantially tubular shape.

In some embodiments, a stainless steel sheath 292 is coupled around the chamber wall 294. In cases where the stainless steel sheath 292 is used, it is preferably not in direct contact with the chamber wall 294 as such contact can cause overheating and melting of the sheath 292. Instead, the interior wall of the sheath 292 is preferably coupled to the faceplate 290, leaving an air gap between the chamber wall 294 and the sheath 292. In order to prevent the air gap from getting hot enough to melt the sheath 292, axial vents 293 can be disposed in the sheath 292 to allow the heat to escape from the air gap between the chamber wall 294 and the sheath 292. It is contemplated that the sheath 292 can be coupled around the chamber wall 294 in a variety of ways. In a preferred embodiment, the sheath 292 is coupled to the faceplate 290, thereby avoiding direct contact with the chamber wall 294. In some embodiments, the sheath 292 is coupled to the faceplate 290 using screws or some other fastening means (not shown). In some embodiments, ceramic screws (not shown) are used at or near the end of the chamber wall 294 opposite the faceplate 290 to support and center the chamber wall 294 within the sheath 292.

In some embodiments, the faceplate 290 is configured to be coupled to the chamber wall 294 prior to being coupled to the plasma gun 202, thereby allowing the faceplate 290 and the chamber wall 294 to be coupled to the plasma gun 202 and de-coupled from the plasma gun 202 as a single unit. In some embodiments, the faceplate 290, the chamber wall 294, and the plasma gun 202 are configured to be coupled together using one or more threaded fasteners. FIG. 2 shows the faceplate 290 being coupled to the chamber wall 294 using threaded fasteners 296. In a preferred embodiment, threaded fasteners 296 pass through the faceplate 290 at a location that does not interfere with channel 270. For example, in FIG. 2, the threaded fastener 296 at the top of the figure is shown being disposed behind channel 270. FIG. 2 also shows the coupling of the faceplate 290 and the chamber wall 294 being coupled to the plasma gun 202 using threaded fasteners 298. In this embodiment, the faceplate 290 and the chamber wall 294 can be de-coupled and removed from the plasma gun 202 as a single unit by loosening fasteners 298 if and when channel 270 and/or port 275 become clogged. A pre-coupled faceplate 290 and chamber wall 294 can then be immediately fastened to the plasma gun 202 using fasteners 298. By configuring the faceplate 290 and the chamber wall 294 to be coupled together separately from the plasma gun 202, the present invention significantly reduces and minimizes the amount of down time that occurs when a channel or port becomes clogged. A clean faceplate/chamber wall coupling can be immediately swapped in to replace the clogged faceplate/chamber wall coupling.

FIG. 3 illustrates one embodiment of method 300 of using a plasma gun and an extension assembly to process powder material in accordance with the principles of the present invention.

At step 310, a plasma gun extension assembly is formed. In a preferred embodiment, the extension assembly comprises a faceplate and an extension tube coupled together, as discussed above with respect to FIG. 2.

At step 320, the extension assembly is coupled to a plasma gun, as discussed above with respect to FIG. 2. In a preferred embodiment, the faceplate of the extension assembly is positioned between the plasma gun and the extension tube as shown in FIG. 2. Furthermore, the extension assembly preferably comprises a port that is configured to introduce powder to an expanded plasma stream at a location outside of the plasma gun and within the extension assembly. In some embodiments, as discussed above, this port is disposed on the faceplate.

At step 330, a plasma stream is generated using the plasma gun. In a preferred embodiment, working gas flows through a gas inlet of the plasma gun, through a gap between an anode and a cathode, and out of an outlet of the plasma gun. At the same time, power is supplied to the plasma gun. The current arcing across the gap energizes the working gas and forms a the plasma stream, which flows out of the outlet and into the extension tube, where the plasma stream expands.

At step 340, a powder is flown into the plasma stream in the extension tube. In a preferred embodiment, the powder flows through a port in the faceplate and is introduced into the plasma stream at a location downstream from the outlet of the plasma gun. The plasma stream entrains and works on the powder, forming a highly reactive and energetic mixture, wherein the powder is vaporized in some embodiments.

At step 350, further processing of this mixture can be performed. For example, in some embodiments, this mixture of vaporized powder moves through the system in the flow direction of the working gas. As it moves, the mixture cools and condensed particles are formed therein. In some embodiments, particles of one type can be coated with particles of another type. In some embodiments, the reactive mixture flows into a quench portion of the extension assembly or a separate quench chamber. One example of a suitable quench chamber is provided in U.S. Provisional Patent Application Ser. No. 61/284,329, filed Dec. 15, 2009, and entitled “MATERIALS PROCESSING.” The quench area preferably comprises a substantially cylindrical surface extending into a frusto-conical surface. The frusto-conical surface narrows to meet an outlet. The frusto-conical surface acts as a funneling surface, channeling conditioning fluid through into a quench region where the reactive mixture is to be conditioned. While the reactive mixture flows into the quench region, conditioning fluid is supplied into the quench region. Preferably, the angle at which the conditioning fluid is supplied produces a high degree of turbulence and promotes mixing with the reactive mixture. This turbulence can depend on many parameters. In a preferred embodiment, one or more of these parameters is adjustable to control the level of turbulence. These factors include the flow rates of the conditioning fluid, the temperature of the frusto-conical surface, the angle of the frusto-conical surface (which affects the angle at which the conditioning fluid is supplied into the quench region), and the size of the quench region. Following injection into the quench region, cooling, and particle formation, the mixture flows from the quench chamber through an outlet port. In some embodiments, suction generated by a generator moves the mixture and conditioning fluid from the quench region into a conduit. From the outlet port, the mixture flows along the conduit, toward the suction generator. Preferably, the particles are removed from the mixture by a collection or sampling system prior to encountering the suction generator.

At step 360, it is determined whether or not the port that introduces the powder into the extension chamber is clogged. If the port is not clogged, then the process continues to generate a plasma stream at step 330 and process powder. If the port is clogged, then the extension assembly is removed from the plasma gun, at step 370, and a new extension assembly is provided. The new extension assembly is then coupled to the plasma gun at step 320, and the process repeats the plasma generation and powder processing steps. Since the extension assembly, comprising the faceplate and the extension tube, is already pre-assembled, it takes very little time to replace the clogged extension assembly. The clogged extension assembly can simply be de-coupled from the plasma gun as a single unit, and the replacement extension assembly can then be coupled to the plasma gun as a single unit.

The present invention has been described in terms of specific embodiments incorporating details to facilitate the understanding of principles of construction and operation of the invention. Such reference herein to specific embodiments and details thereof is not intended to limit the scope of the claims appended hereto. It will be readily apparent to one skilled in the art that other various modifications may be made in the embodiment chosen for illustration without departing from the spirit and scope of the invention as defined by the claims. 

What is claimed is:
 1. A method of using a plasma gun system, the method comprising: generating a plasma stream using a plasma gun, wherein the plasma stream flows through an outlet of the plasma gun and into an extension chamber having an interior diameter defined by a chamber wall, the plasma stream expanding upon entering the extension chamber; and flowing a powder into the expanded plasma stream in the extension chamber via a port fluidly coupled to the extension chamber, wherein the port introduces the powder to the expanded plasma stream at a location outside of the plasma gun.
 2. The method of claim 1, wherein the port is disposed on a faceplate that is coupled between the plasma gun and the extension chamber.
 3. The method of claim 2, wherein the faceplate comprises a circular ring shape and the outlet of the plasma gun is aligned with the center of the faceplate to enable the plasma stream to pass the faceplate and flow into the extension chamber.
 4. The method of claim 2, wherein the faceplate comprises copper.
 5. The method of claim 2, wherein the chamber wall comprises a ceramic material.
 6. The method of claim 5, wherein the chamber wall comprises boron nitride.
 7. The method of claim 2, wherein the chamber wall comprises a substantially tubular shape.
 8. The method of claim 2, wherein a stainless steel sheath is coupled to the faceplate and around the chamber wall.
 9. The method of claim 2, wherein the faceplate is configured to be coupled to the chamber wall prior to being coupled to the plasma gun, thereby allowing the faceplate and the chamber wall to be coupled to the plasma gun and de-coupled from the plasma gun as a single unit.
 10. The method of claim 9, wherein the faceplate, the chamber wall, and the plasma gun are configured to be coupled together using one or more threaded fasteners.
 11. A plasma gun system comprising: a plasma gun comprising an outlet, wherein the plasma gun is configured to generate a plasma stream and provide the plasma stream to the outlet; and a plasma gun extension assembly configured to be coupled to the plasma gun, wherein the plasma gun extension assembly comprises an extension chamber and a port, the extension chamber having an interior diameter defined by a chamber wall and being configured to receive the plasma stream from the outlet of the plasma gun and to enable the plasma stream to expand upon entering the extension chamber, and the port being configured to introduce a powder to the expanded plasma stream at a location outside of the plasma gun.
 12. The system of claim 11, wherein the port is disposed on a faceplate that is coupled between the plasma gun and the extension chamber.
 13. The system of claim 12, wherein the faceplate comprises a circular ring shape and the outlet of the plasma gun is aligned with the center of the faceplate to enable the plasma stream to pass the faceplate and flow into the extension chamber.
 14. The system of claim 12, wherein the faceplate comprises copper.
 15. The system of claim 12, wherein the chamber wall comprises a ceramic material.
 16. The system of claim 15, wherein the chamber wall comprises boron nitride.
 17. The system of claim 12, wherein the chamber wall comprises a substantially tubular shape.
 18. The system of claim 12, wherein a stainless steel sheath is coupled to the faceplate and around the chamber wall.
 19. The system of claim 12, wherein the faceplate is configured to be coupled to the chamber wall prior to being coupled to the plasma gun, thereby allowing the faceplate and the chamber wall to be coupled to the plasma gun and de-coupled from the plasma gun as a single unit.
 20. The system of claim 19, wherein the faceplate, the chamber wall, and the plasma gun are configured to be coupled together using one or more threaded fasteners. 